In recent years, plant extracts have become the focus of corrosion inhibitor research due to their low toxicity, easy availability and economical preparation. This review presents most of the recent contributions made to the application of plant extracts as corrosion inhibitors for steel in sulphuric acid, as well as in both hydrochloric acid and sulphuric acid. The constituents, properties, adsorption modes and inhibition mechanisms of these natural products are discussed. Evaluation methods and the factors that influence the corrosion-inhibition efficiency of plant extracts are also summarised. 相似文献
A liquid chromatographic method was developed for the simultaneous quantification of four major active components in tobacco (Nicotiana tobaccum L.) wastes. Samples were extracted with 70% v/v aqueous methanol, four compounds including chlorogenic acid, cryptochlorogenic acid, neochlorogenic acid and caffeic acid were identified and determined by using LC coupled to electrospray tandem mass spectrometry and LC–UV method, respectively. Separation in LC–UV was on an Alltima C18 column (250 mm × 4.6 mm i.d.; 5 μm) with a mobile phase consisting acetonitrile: ammonium acetate buffer (pH 4.5) (5:95 v/v), at a flow rate of 1.0 mL min−1, detected at 327 nm. Four regression equations showed good linear relationships (r2 > 0.999) between the peak area of each marker and concentration. The method has good repeatability and precision, the intra-day and inter-day RSD for both retention time and peak area was less than 1.0%. The recoveries, measured at three concentration levels, varied from 96.33 to 101.10%. The LOD (S/N = 3) and LOQ (S/N = 6) were less than 0.010 and 0.795 μg·mL−1, respectively. This assay was successfully applied to the determination of four active compounds in ten samples. The results indicated that the developed assay method was rapid, accurate, reliable and could be readily utilized as a quantitative analysis method for various of tobacco wastes.
In a weak acid medium, some aminoglycoside antibiotics, such as kanamycin (KANA), gentamicin (GEN), tobramycin (TOB) and neomycin (NEO), or acid bisazo dye Evans Blue (EB) can only produce very weak resonance Rayleigh scattering (RRS) signals. However, when two agents react with each other to form ion-association complexes, the RRS intensity can be greatly enhanced and a new RRS spectrum with a significant enhancement of the RRS intensity in the wavelength range from 350 nm to 600 nm can be observed. The maximum scattering peak is at 570 nm. There is a linear relationship between the RRS intensity and the antibiotic concentration in the range of 0.01-6.0 microg mL(-1) at 570 nm. This RRS method for the determination of aminoglycoside antibiotics at trace-amount levels has been developed. The detection limits (3sigma) of the four antibiotics, whose order of sensitivity from high to low ranks as KANA > NEO > TOB > GEN, are 5.2-6.9 ng mL(-1). This method has good selectivity and has been successfully applied to the quick determination of antibiotics not only for injections and ear drops, but for clinic serum samples as well. In addition, the reaction mechanism by using a quantum chemistry method and the influencing factors of the RRS spectra and the enhancement reasons of RRS have been discussed. 相似文献